The 35-year-old has missed just one of his team's 34 Premier League games this season, helping the Merseyside outfit make a sustained bid for a top-four finish.
And the former Manchester United keeper, who has won 97 caps for the United States, has been rewarded for his excellent form with a new deal.
Everton manager Roberto Martinez expressed his delight at securing Howard's services for another four years.
"It is fantastic news," Martinez told evertontv. "To have Tim Howard performing as he has been this season, I cannot see past him to choose the best goalkeeper in the league.
"For him, in such an important year with the World Cup around the corner, to commit his future for the long term is an incredible moment for the dressing room."
Everton's hopes of securing a UEFA Champions League berth suffered a blow on Wednesday when they suffered a surprise 3-2 home loss to Crystal Palace.
Howard and his team-mates will hope to bounce back from that setback when they host his former club United at Goodison Park on Sunday.
